Traditionally ferrite cores, cores cut out from thin metal sheets, and compacted powder magnetic cores, are used as magnetic cores for choke coils subject to high frequencies. Metal magnetic materials provide an advantage over ferrite in that they can achieve higher saturation magnetic flux densities. On the other hand, metal magnetic materials themselves have low insulation property and must be given insulation treatment. Patent Literature 1 proposes compression-molding a mixture of Fe—Al—Si powder having surface oxide film with a binder, and then heat-treating the molded product in an oxidizing atmosphere. According to this patent literature, applying heat treatment in an oxidizing atmosphere allows for formation of an oxide layer (alumina) in areas where the insulation layer on the surface of alloy powder has broken during compression molding, thereby achieving a complex magnetic material offering good DC superimposition characteristics with small core loss. Patent Literature 2 describes a laminated electronic component whose main ingredient is metal magnetic powder, wherein said laminated electronic component is produced by stacking a metal magnetic layer formed by metal magnetic paste containing glass, with conductive patterns formed by conductive paste containing silver or other metal, thereby forming coil patterns inside the laminate, and wherein this laminated electronic component had been sintered in a nitrogen atmosphere at a temperature of 400° C. or above.